1. Field of the Invention
The present invention relates to laminate compositions of polyurethane and specific polymeric membranes and a substrate. The present laminate compositions are useful in construction for forming in place waterproof coverings for walls and especially for roofs.
2. Related Art
Various polymeric membranes (i.e., films or sheets are now being widely used for the purpose of providing waterproof roofing cover, replacing to a large extent asphalt treated felt, particularly in commercial structures. These materials are currently put in place in three ways, i.e., loose, partially adhered and fully adhered.
The predominate system is loose-laid which is ballasted, for example, with stone. The stone may be held in place by coating the loose membrane with tar (asphaltic material) then applying the stones, just as felt has been held in place for years. This system is reputed by some members of the roofing industry to be the current best system, however, just as with the old felt roofs, the stones loosen and the asphalt degrades resulting in a leaky roof, whereas the polymer membrane is still intact. It should also be appreciated that the presence of the stones requires a relatively heavy membrane (e.g. 40 mils) to prevent punctures from the stones. A modification of this system is a mechanical ballast wherein, for example, strips of metal are laid over the membrane and affixed (e.g., by screws) to the roof substrate. Usually in these systems the seams would be lapped and solvent or adhesive bonded and lap point caulked. Such a system is described in U.S. Pat. No. 4,162,597.
The partially adhered systems presently used solvent adhesives which are applied along each edge of each membrane, lapped and caulked as for the ballasted systems. The fully adhered systems also use solvent adhesives applied over the entire area of the membrane between the membrane and roof substrate. This system avoids the ballast but is generally considered to be too costly in that the solvent adhesives are expensive, do not obtain a good adherence, contain flammable solvents and are more labor intensive. Primers should be used, which further increase the cost.
Another problem using any of the current systems is that grooves, corrugations, and the like may be left as voids within the covering, hence a weaker roof covering is obtained and one, if punctured will allow a buildup of water between the membrane and the roof substrate and/or leaking.
It is also well known that polyethylene, polypropylene and copolymers of these materials will not bond to foamed in place polyurethane, in fact, these polymer membranes are used as release films for polyurethane foams. It has been found by the present inventor that membranes comprising polymers of ethylene, propylene and/or mixtures thereof that are modified in specific ways, do adhere to polyurethane foam when foamed in place and contacted therewith during the foaming operation.
It is a specific advantage of the present laminate composition that it forms a monolithic structure, which can be prepared in place, for example, on a roof or a wall. A feature of the laminate compositions is that they furnish insulation to the substrate. It is a very great advantage that the laminate forms a superior moisture barrier, even if the membrane is punctured, the urethane foam is a closed cell structure (in the sense that the cell walls are substantially 100% intact). Another significant advantage of roofs completed with the present laminate compositions is the elimination of the billowing effect and wind uplift possible with some of the systems described above. These and other advantages and features will become more apparent from the following descriptions.